> That's even more of a no-brainer, as an average 9-5 has practically zero upside, so your net worth is likely to stay flat (if not even go down).

The average millionaire is just a schmuck with a high paying 9-5 job. Doctors, lawyers, engineers, generic corporate drones etc. I don't know where you got the idea that it's impossible to make more than a subsistence wage with a W2 job but you are wrong.